1. Field of the Invention
The present invention relates to a urethral stent assembly. More specifically, the invention relates to a continent urethral stent assembly which can be used for treating and preventing urethral stricture following surgery, without the disadvantage of losing control on urination that all other types of catheter stents would have.
2. Related Art
The male urethra is a narrow membranous canal, extending from the neck of the bladder to the meatus urinarius at the end of the penis. The neck of the bladder is the point of commencement of the urethra. There is no tapering part, which would constitute a true neck. The bladder suddenly contracts to the opening of the urethra. The sphincters are located immediately below the neck of the bladder and around the commencement of the urethra. Their function is to shut off the bladder when the person is not urinating.
Urethral stricture is one of the oldest ailments reported to afflict man. Historically, the predominant cause was gonococcal urethritis, a disease presently enjoying a resurgence. With increased awareness of its danger, and with earlier and more appropriate treatment, the impact this disease has on the urethra has lessened in modern communities. The modern surgical era, particularly in recent years, has seen a significant change in the management of the disease.
After surgical correction of urethral stricture, followed by rejoining of the ends of the urethra, as well as after other similar surgical procedures affecting the urethra, there is a great natural tendency for the affected part of urethra to collapse and heal with scar tissue. Some patients will develop strictures again and require further surgery.
Urethral stents have long been used as a non-surgical alternative to the treatment of the symptoms of obstructive prostatism. U.S. Pat. No. 5,007,898 issued to Rosenbluth et al discloses an apparatus comprising an expandable dilatation catheter 18, a sheath 12, a dilatation balloon 62, a locating balloon 60, a flexible distal tip 14, a stylet 154, etc. The catheter is inserted into the urethra and remains within the irrigation conduit until the locating balloon is disposed within the bladder, at which time the stylet is removed. The locating balloon is inflated by an inflation conduit coupled to a source of pressurized fluid to force open the affected prostatic urethra and eliminate the obstruction.
Urethral stents have also been used to facilitate bladder drainage in individuals who are unable to initiate or control such drainage due to organic disability, immobility, or other physical impairment. U.S. Pat. No. 4,932,938 issued to Goldberg et al discloses a urethral indwelling catheter with incontinence control having a manually-manipulable control valve for controlling bladder drainage.
A stent placement instrument and method is disclosed by U.S. Pat. No. 5,078,720 to Burton et al. The Burton instrument comprises an elongated inner tube having an outer tube disposed along its axis adapted to carry and retain a self-expanding stent adjacent its proximal end, and an arrangement for releasing the stent, in combination with at least one of the following components: (a) a location member for positioning and fixing the instrument so that the stent is released at a desired location in the body canal, and (b) a member for releasing the stent in a retrograde manner. A method for placing a self-expanding stent in a body canal is also disclosed.
Other stents developed for use in urethra include the Urolume Wallstent developed by Medinvent and supplied by American Medical System, and an intra-prostate stent sold by Advance Surgical Intervention. However, these stents are made of metal wire mesh. They are left in the urethra permanently and therefore are subject to inherent complications resulting from leaving a foreign object in the body.
Structurally related to urethral stents is a gastrostomy tube disclosed by U.S. Pat. No. 3,915,171 to Shermeta. The gastrostomy tube is intended for insertion into the stomach to supply and remove fluid. The device comprises a conduit 45, first retention bulb 25, 35, second retention bulb 40, first closure means 20 and second closure means 47. The two bulbs structurally embrace the two walls to prevent leakage from the stomach and from and into the abdominal cavity. The device is preferably made entirely from medical grade silicone rubber.
The insertion and operation of the prior art stents are very cumbersome. Special instruments are required to insert and remove the stents. Additional apparatus has to be attached to inflate the balloon commonly used to retain prior art stents in place in the bladder. Users of the prior art stents cannot have normal control over urination. Thus, there is a need for a simple method and apparatus to effectively treat and prevent urethral stricture without the loss of normal control over urination.